Some specific imaging methods and, especially, imaging apparatuses designed for said methods have generally been used for x-ray imaging the human cranial area. Simplest of these as far as technology of the apparatus and of the imaging itself are concerned are solutions related to transillumination imaging in which, during an exposure, both the patient and the imaging means remain stationary. Thus, imaging of this kind has not always been implemented even such that the means for generating radiation and receiving image information would have been arranged as a physically integrated apparatus. On the other hand, e.g. in odontological panoramic imaging, controlling of the relative movement between the imaging means and the object being imaged plays an essential role, as well as does controlling of movement of a film or operation of a detector during exposure. A typical panoramic x-ray imaging apparatus is based on a structure in which a source of radiation and a receiver of image information are located at the opposite ends of the so-called C-arm, which is arranged movable. In one typical CT imaging, again, imaging means arranged inside a so-called gantry or an O-structure are moved within said structure while the patient is lying e.g. on a table belonging to the imaging apparatus, the table extends inside the gantry. Conventionally in these arrangements, either said table or the gantry itself is arranged movable to enable moving of the patient with respect to the imaging apparatus.
The medical use of computed tomography has broadened, inter alia, as a result of the so-called cone-beam tomography becoming more common such that, on the market, apparatuses have begun to emerge which have been specifically designed in view the needs of odontology and, on the other hand, orthopaedics, for example. Typically, these apparatuses are not as massive and as expensive as the conventional computed tomography apparatuses used in hospitals have been.
In apparatuses, in which a person has to be positioned inside a closed structure for the duration of an exposure, problems may occur due to claustrophobia suffered by some people. This problem is naturally potentially the greater the smaller the space within which the patient is to be positioned.
Even though computed tomography is in principle able to create voxel data of the whole volume being imaged, it has been noted that depending on the case some parts of an anatomy may become imaged more sharp than others. On the other hand, it is also known that some human tissues are more sensitive with respect to a radiation load than some others.